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Montana Field Guide

Montana Field Guides

Johnston's Knotweed - Polygonum sawatchense
Other Names:  Polygonum douglasii ssp. johnstonii

Status Under Review
Native Species

Global Rank: GNR
State Rank: SNR

Agency Status
MNPS Threat Rank:

External Links

General Description
Annual. Stems erect, simple or branched at the base, 5–35 cm. Leaves short-petiolate; blades 8–20 mm long, linear-oblong, reduced above; stipules lacerate, 2–10 mm long. Flowers 3–4 mm long, 1 to 4 in leaf axils; pedicels erect, 1–4 mm long; tepals green with white to pink margins. Achene 3-sided, 2–3 mm long, shiny black (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range

Range Comments
BC to SK south to CA, AZ and NM. One collection from an alpine, stony, calcareous slope in Beaverhead County (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 3

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)


The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus bifarius, Bombus flavifrons, Bombus frigidus, Bombus melanopygus, Bombus sylvicola, Bombus occidentalis, Bombus pensylvanicus, Bombus insularis, and Bombus kirbiellus (Macior 1974, Colla and Dumesh 2010).

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141: 39-68.
    • Macior, L.M. 1974. Pollination ecology of the Front Range of the Colorado Rocky Mountains. Melanderia 15: 1-59.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
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Citation for data on this website:
Johnston's Knotweed — Polygonum sawatchense.  Montana Field Guide.  .  Retrieved on , from